452 r. W. GAMBLE AND J. H. ASHWORTH. 



5. Epidermis. 



The "cuticle" is well developed in all species of A renicola, 

 but perhaps most abundantly in A. ecaudata and Grubii. 

 It is formed by the mucus cells of the epidermis. In 

 post-larval specimens of the common lugworm the " cuticle " 

 forms a distinct gelatinous envelope or tube, which in- 

 vests the body closely and does not impede the swimming 

 movements, but appears to bend with each undulation and to 

 be readily cast off. In post-larval A. cristata the envelope 

 is described as " small masses of a soft gelatinous substance 

 in which the animals creep actively about" (Wilson, 1883). 

 In A. ecaudata at the abranchiate stagfe a similar tube is 

 formed, and is attached to algae (Fauvel, 1899), but this is dis- 

 puted by Mesnil. The cells which secrete this covering are 

 at first confined to certain broad bands which alternate with 

 non-glandular zones. Rough handling of adult specimens 

 of A. ecaudata and A. Grubii induces an increased forma- 

 tion of this mucous secretion, accompanied by a yellow colour- 

 ing matter which readily stains the hands. There are, in 

 fact, two kinds of pigment, — a yellow (orin adult A. marina 

 green) pigment, soluble to some extent in sea water and 

 especially in alcohol, and probably of lipochrome nature ; and 

 an insoluble black pigment resembling melanin in its resist- 

 ance to solution. Both these appear in early post-larvae, to 

 which they give a characteristic colour. We have not, 

 however, examined these pigments in detail. In adult 

 specimens of A. Grubii and A. ecaudata the epidermis is 

 pi'oduced into ridges and furrows, resulting in the annulation 

 and areolation of the skin. In the ridges the mucus cells 

 ai'e abundant, in the furrows they are absent; but in both 

 positions the long cylindrical epidermal cells are almost filled 

 with granules of an insoluble brown pigment, which appears 

 black in the aggregate. Theyextendon to theprostomium, and, 

 in fact, are present all over the epidermis, though to a less 

 extent in the nuchal groove than elsewhere. In A. Grubii 

 masses of this melanin-like pigment are actually found in 



